Cleaning composition derived from potato processing wastes

ABSTRACT

A process for the preparation of a cleaning composition from potato processing wastes comprises forming a digest of potato wastes in caustic alkali, reacting animal or vegetable oil, preferably potato processing waste oil, with caustic alkali for form a liquid soap and cooking an 80:20 - 40:60 blend of liquid soap to potato digest at 180 - 212° F. for from 30 - 60 minutes to form a cleaning composition concentrate. The concentrate is preferably filtered to remove fibrous material and other solids after which it may be modified with conventional additives and diluted, the additives and degree of dilution depending upon the ultimate intended usage and preferred physical form of the composition.

The present invention relates to organic cleaning compositions and, moreparticularly, to cleaning compositions prepared from vegetable starches.

There is a need today for cleaning compositions which can beinexpensively prepared in a simple manner from readily availablematerials. Moreover, present day cleaning compositions must beenvironmentally safe, i.e., they should be readily biodegradable and, atthe same time, possess a low nutrient level.

It is therefore an object of the present invention to provide amulti-use cleaning composition made from readily available vegetablestarch.

It is another object of the invention to provide a cleaning compositionreadily made from vegetable starch waste matter, particularly potatoproduction waste.

It is still another object of the invention to provide a cleaningcomposition, and a method of producing same, which composition isreadily biodegradable and low in nutrients.

Other objects and advantages will become apparent from the followingdescription and appended claims taken in conjunction with theaccompanying Figure which is a schematic representation of a preferredform of the process of the present invention.

Briefly stated, in accordance with the aforesaid objects, the cleaningcomposition of the present invention is prepared by heating an aqueousmixture of potato processing wastes, including starch, oils and causticalkali, at elevated temperatures and thereafter adding to the cookedmixture chemical modifiers and diluents in appropriately smallquantities to formulate the desired final cleaning product in thedesired physical form, e.g., liquid granular, bar soap, flake or otherphysical form of cleaning compound for specific and/or specializedpurposes.

The primary composition forming ingredient is the vegetable starch whichis desirably obtained from a low-protein starch source such as corn,wheat, rice or tapioca. Tubers of all types are preferred, such aspotato peelings, culls, whole Irish potatoes, and the like. At present,potato processing plants separate, e.g., by screening, settling, vacuumfiltration and skimming, the processing wastes and dispose of them asanimal feed, as grease for rendering plants, as soil enhancers, and thelike. Of course, waste quantities and methods of disposition vary fromplant to plant depending upon the degree of recycling practiced withinthe plant, the particular production process practiced at the plant,plant location, land availability, proximity of animal farms, etc.Nevertheless, it has been found that the use of potato plant wastes,either as the totality of raw starting materials or as somesignificantly large fraction thereof, to prepare a cleaning compositionconcentrate has very favorable economics. This is particularly so sincethe vegetable starch source may take any physical form. For example,potatoes, in addition to the forms set forth above may be cut, peeled,shredded or mashed. If the vegetable starch source has an insoluble skinor hull, the insoluble material can be readily removed by filtrationduring processing. For the purpose of this application, the term "starchcontaining potato processing wastes" is defined as the vegetable starchwaste material from potato processing plants which contains appreciablequantities of potato starch.

The raw starting materials for the present process are all readilyavailable as the prevalent constituents of potato processing plantwastes. An exemplary breakdown of wastes produced at a typical lyepeeling, fried potato product plant is set forth below:

Waste Materials from a Potato Processing Plant

1. Reject Potatoes and other Potato Starch Waste:

Approx. 0.5 ton Waste/1.0 ton of Raw Potatoes processed

2. Potato Waste Breakdown

Approx. 30% -- Peewees (small potatoes)

60% -- Solids from Screening and Vacuum Filtration

10% -- Lost in Primary Effluent

3. Caustic Waste:

Approx. 5 lbs. (as NaOH)/1.0 ton of Finished Potato Product

4. Oil and Grease Waste:

Approx. 35 lbs./1.0 ton of Finished Potato Product

5. Water Use:

Approx. 1400-3000 gallons/1.0 ton of Raw Potatoes Processed

Only two alkalies are believed to be economically practical for use inpreparing the cleaning compositions of the present invention. Sodiumhydroxide is the preferred alkali because it is least expensive and mostreadily available. Potassium hydroxide is also suitable but is somewhatmore expensive and not as readily available. However, potassiumhydroxide is particularly advantageous if the end product is to be aliquid soap since potassium soaps are fully soluble in water to giveliquid soap solutions containing up to 25% solids. Some sodium soaps onthe other hand, especially the stearates, form gels in water solution.Ammonium hydroxide and calcium hydroxide, for example, are not suitablefor use because the former is not a strong enough alkali while thelatter forms an insoluble precipitate with fatty acids. The amount ofalkali employed depends upon a number of factors --primarily upon theamount of starch material present, but also upon the starch form and itswater content. Generally, however, sufficient alkali should be used togive the final concentrated product a pH of 10 - 11. This pH objectivecan usually be obtained with a weight ratio of caustic to starch ofabout 1:6.

Nearly any fatty acid source, such as animal fats or vegetable oils, canbe used in the present process to form the instant cleaning compositionalthough the waste oils from potato processing are preferred from thestandpoint of economics. While fats such as tallow and coconut oil aregenerally preferred in the industry, according to the present inventionwhich employs an unusually large proportion of starch compared toconventional processes, the choice of fat is less important for controlof cleaning composition properties. Exemplary suitable animal fatsinclude pure lard (pork) and beef fats (suet). Among the usefulvegetable oils are peanut oil, olive oil, corn oil, soybean oil, and thelike.

To prepare the cleaning compositions of the present invention thevegetable starch, such as potato or potato waste is pulped, ground,crushed or otherwise pulverized or particulated, and caustic alkali isadded thereto to form a liquid potato digest. Inasmuch as the quantityof alkali employed is dependent upon a number of variables, it isrecommended that preliminary tests be conducted to ascertain therequisite alkali quantity to provide a pH 10 - 11 concentrated productwith the particular vegetable starch source material selected. Inaddition to pulverizing and/or particulating the vegetable starch, thepulping or grinding operation also renders the starch, thereby assistingits solutioning with the alkali. The resulting potato digest orliquefied starch is admixed in suitable proportions, depending upon thedesired properties of the finished product, with a liquid soap solutionwhich is prepared by reacting the vegetable or animal oil, preheated to135° - 150° F., preferably about 140° F., with a thin stream of caustic.The potato digest-liquid soap admixture is then uniformly cooked insuitable apparatus, such as a steam jacketed cooker, at atmosphericpressure in an air environment at temperatures up to about 212° F.,preferably 180° - 212° F. Exemplary of the apparatus that can be used inthe present process is the apparatus disclosed in copending applicationSer. No. 316,686, filed Dec. 20, 1972 for Food Preparation andDispensing System, now U.S. Pat. No. 3,945,534. The precise temperatureselected for the cooking is itself unimportant, it being dependent inlarge part upon the selected cooking time. However, an exemplarytime-temperature combination found generally satisfactory for cookingthe admixture is about 212° F. for from 30 minutes to one hour. Duringthe cooking, air is preferably blown through the cooker to causeagitation and, at the same time, to cause some degradation of the starchby oxidation. Simultaneous mechanical agitation of the admixture is alsodesirable.

The properties of the resulting concentrated potato soap product depend,in part, upon the proportions in which the potato digest solution andthe liquid soap solution have been blended. It has been found that asatisfactory product can be formed by blending the liquid soap to potatodigest (liquid starch) in a weight ratio of from 80:20 to 40:60 on a drysolids basis. At low soap properties, the cleaning compositionconcentrate is pasty. However, as the proportion of liquid soapincreases, the tendency of the composition to form a firm gel alsoincreases. On the other hand, the foaming properties of the compositionappear to improve with increased proportions of liquid potato digest.Best results in terms of the physical consistency and foaming propertiesof the concentrated cleaning product appear to be attained at a liquidsoap to liquid potato digest weight ratio of about 60:40 on a dry solidsbasis.

Although the cleaning composition concentrate has been formed at thecompletion of the cooking step, it is desirable at that point in theprocess to remove any undigested potato materials, such as excessfibrous material, skin residue, lignocellulose and excess starchgranules, by filtration or equivalent removal technique. It has beenfound, however, as a practical matter, that it is undesirable andunnecessary to attempt to remove all undigested potato materials sincethe materials tend to pack during filtration to form a poorly permeablefilter cake causing subsequent filtration to be uneconomically slow. Itis therefore recommended that only limited filtration be attempted. Inthis connection filtration through a centrifugal extracting sieve, suchas a 28-mesh self-cleaning screen, has been found to be satisfactory interms of balancing production economies with the desirability ofremoving excess solids. The filtered material has some value as animalfeed and can often be profitably disposed of in that fashion. Thefiltrate is the concentrated cleaning composition of the presentinvention, substantially free of undesirable excess solids, which caneither be used as is or, more desirably, can be modified by the additionof appropriate chemicals and diluents to form commercially practicalproducts. Exemplary of chemical additives are the well known coloring orscenting additives, foaming agents, brighteners, and the like. For mostpurposes the concentrated composition is preferably diluted with water,for example in ratios of from 1:8 to 1:10 concentrate to water,depending upon the intended ultimate use. Such dilution generallyreduces the pH of the composition to the range 9 - 10 and, in suchaqueous form, the composition is useful, for example, as a laundrydetergent, surface cleaner (e.g., sinks, walls, counters, painted andmetallic surfaces), dishwashing detergent, hand soap, floor cleaner,shampoo, or in most any other application where soap is generallyuseful.

The accompanying FIGURE of the Drawing depicts a typical process for theproduction of the cleaning compositions of the present invention frompotato processing wastes.

Referring to the FIGURE, it can be seen that potato wastes, such asculls and scraps, are initially particulated or pulverized in pulper 12to reduce the particle size and thereby to enhance the liquefication ofthe starch component. The particulated potato wastes together with thepreferred sodium hydroxide or potassium hydroxide caustic are admixed inTank #1 at ambient temperature to form a potato digest. The relativeproportions of potato waste to caustic should be in the range of 9 to 11parts by weight dry caustic to each 100 parts dry potato solids, theprecise quantity of caustic in each case depending upon factors such asmoisture content of the wastes, ultimate intended product and the like.Water is added as necessary to assure a water content in Tank #1 of from40 to 60 parts water per 100 parts potato solids. One exemplaryadmixture in Tank #1 includes 10 parts dry sodium hydroxide to 100 partspotato solids and contains 40 parts water.

In Tank #2, waste potato oils from potato processing are preheated tothe range 135° to 150° F., preferably 140° F., and are contacted andreacted with a thin stream of caustic. The relative quantities of oiland caustic should be in the range 9 to 11 parts dry caustic per 100parts by weight oil. Water is also present in Tank #2 in amounts rangingfrom 25 to 28 parts by weight water per 100 parts by weight oil. The oiland caustic react to raise the temperature in Tank #2 to the range about190° - 212° F. and to form a liquid soap solution.

The potato digest from Tank #1 and the liquid soap from Tank #2 aremetered, respectively, through valves 14, 16 in appropriate quantitiesas hereinbefore set forth, and directed to a cooking chamber 18 wherethe mixture can be heated to 180° - 212° F. for about 30 - 60 minutes toform the concentrated potato soap composition of the present invention.Air or equivalent oxidizer is bubbled through the mixture to provideagitation and to assist in the degradation of the starch. Mechanicalagitation (such as furnished by agitator 20) may also be provided.Preferably, the chamber is a steam-jacketed cooker such as is disclosedin aforementioned U.S. Ser. No. 316,686, filed Dec. 20, 1972.

The potato soap concentrate is pumped from chamber 18 through outletcontrol valve 22 via pump 24 into a self-cleaning screen filter unit toremove potato skin residues, fibrous matter, undigested starch and otherpotato solids which may be present. The soap concentrate of the presentinvention (filtrate) is fed to Tank #3 wherein any number ofconventional additives, e.g., A, B, C, D, may be admixed with theconcentrate and, at the same time, the concentrate can be diluted tofinal product form. Of course, in accordance with known practice, theextent of dilution and the identity and quantity of the additivesemployed depend upon the desired physical form and intended usage of theend product. The end product is permitted to cool the ambienttemperature, usually in a large tank, for at least 24 hours to permit itto set-up.

EXAMPLE I

Using the process of the present invention, potato culls and scrapshaving a moisture content of about 92% water were admixed with drysodium hydroxide in a ratio of 10 parts of dry sodium hydroxide per 100parts of dry potato solids. An additional quantity of 40 parts of waterper 100 parts of dry potato solids was also added and the aqueouspotato-caustic solution was admixed to form a potato digest. In aseparate tank, waste potato processing oils were heated to 140° F. andreacted with 10 parts of dry sodium hydroxide per 100 parts of oil toform a liquid soap. The liquid soap and potato digest were respectivelymetered into a steam-jacketed cooking chamber in the weight ratio of60:40 soap to digest on a dry solids basis. Air was passed through thechamber and the soap-digest was mechanically agitated while being heatedfor 30 minutes to about 212° with 212° F. steam passing through thechamber jacket at atmospheric pressure. The resulting product wasscreened through a centrifugal extracting 28 mesh sieve and the filtratewas diluted with 8 parts water per part filtrate. The resulting productwhich was about 94.8% liquid and 5.2% solids, was stored in a large tankand permitted to cool for about 24 hours during which time it hardenedto set-up.

EXAMPLE II

The potato soap composition filtrate from Example I was analyzed toinclude volatiles by oven drying at 105° C, ash at 550° C, alkalinity bytitration with standardized HCl, pH by a Beckman pH meter, surfacetensions by du Nuoy tensionmeter, fatty acids by extraction of theacidified product, undissolved solids by centrifugation of aqueousdilution of the product, solidifying points by thermometer, and traceelements by emission spectrograph. Sodium was calculated from the ashanalysis, glycerol was calculated from the fatty acids and the totalstarch plus other trace components were calculated by difference. Theresults are given in Table I.

                  Table I                                                         ______________________________________                                        Analysis                                                                      ______________________________________                                                          Composition                                                                     As Received Dried                                         ______________________________________                                        Volatiles (water)   84.5        --                                            Nonvolatiles, fatty acids                                                                         8.9         58                                            sodium ion          2.2         14                                            glycerol            1.0          6                                            starch, etc.        3.4         22                                            Total               100.0       100                                           Ash                  5.0%                                                     Undissolved solids (approximate)                                                                   2.6%                                                     Alkalinity           740 meq g.sup.-1                                         pH                   12.0                                                     Solidifying point    49° C (first gel)                                                      42° C (solid)                                     Surface tension (1% solution)                                                                      29.8 dynes cm.sup.-1                                     (0.1% " )            30.0 "                                                   (0.01% " )           46.1 "                                                                  Element   Approximate Amount                                   ______________________________________                                        Ash Analysis   sodium    Major component                                      (qual spectrographic)                                                                        silicon   1%                                                                  lead      .1%                                                                 aluminum  "                                                                   calcium   "                                                                   magnesium "                                                                   zinc      .01%                                                                silver    "                                                                   strontium "                                                                   Phosphorus                                                                              trace                                                               iron      "                                                                   copper    "                                                                   potassium "                                                    ______________________________________                                    

The filtrate composition dispersed in hot water easily and gelled uponcooling. The undiluted product (15% solids) on cooling started to gel at49° C and became solid at 42° C. A dilute solution upon cooling formed astiff gel down to 0.67% solids and a liquid with some gel strands downto 0.09% solids.

For some purposes, the potato soap product thus far described is ofinsufficient purity and further refining is desirable. The refining maytake place at the same location at which the potato soap was prepared orat a remote location. To refine the potato soap, it should be heated ina tank to about 150° F. to liquefy the soap and an alkali, such assodium or potassium hydroxide, added to the heated soap in quantities offrom 1/2 to 1 pound of dry alkali per each 10 pounds of potato soap,preferably in a ratio of alkali to potato soap of 1 to 10. The precisequantity of alkali added will depend upon the degree of hardness desiredin the final soap product. Approximately 25% by volume of water is thenadded to the alkali-soap mixture (although there is nothing criticalabout the extent of water dilution for purification purposes, 25% byvolume appears to be an advantageous quantity from the standpoint of therelative strength of the final liquid cleaner product) and the resultingaqueous mixture maintained at a 212° F. rolling boil for about 12 to 15minutes. If desired, air can be metered into the mixture to eliminateboiling over.

The refining process converts the potato soap to a high purity, veryfine grade solid soap which floats to the surface of the aqueousmixture. The remaining liquid constitutes an excellent low sudsingcommercial liquid cleaner which will not gel upon cooling, i.e., it willremain a liquid. The liquid cleaner may be readily separated from thehigh purity soap by draining the liquid through a drain tap located nearthe base of the tank.

While the present invention has been described with reference toparticular embodiments thereof, it will be understood that numerousmodifications can be made by those skilled in the art without actuallydeparting from the scope of the invention. Accordingly, allmodifications and equivalents may be resorted to which fall within thescope of the invention as claimed.

What is claimed as new is as follows:
 1. A process for preparing a soapconcentrate from potato processing wastes comprising the steps of:(a)mixing pulverized starch-containing potato processing wastes with analkali selected from the group consisting of sodium and potassiumhydroxide in the presence of water to form a liquid potato digest; (b)reacting a fatty acid source selected from the group consisting ofanimal fats and vegetable oils with an alkali selected from the groupconsisting of sodium and potassium hydroxide at a temperature in therange 135° - 150° F. to form a liquid soap; (c) admixing said liquidsoap and potato digest in a weight ratio of from 80:20 to 40:60 on a drysolids basis; (d) heating said admixture in the presence of oxygen at atemperature in the range 180° - 212° F. for from 30 to 60 minutes toform a concentrated biodegradable cleaning composition; (e) additionallyheating the concentrated cleaning composition to about 150° F.; (f)adding from one-half to one pound of dry caustic selected from the groupconsisting of sodium and potassium hydroxide for each ten pounds ofconcentrated cleaning composition; (g) diluting the mixture resulting in(f) with water; (h) boiling the resulting aqueous mixture; and, (i)permitting the boiled mixture to cool and to separate into a solid soapportion and a liquid cleaner portion.
 2. A process as claimed in claim1, wherein said concentrated cleaning composition in step (d) exhibits apH in the range 10 to
 11. 3. A process, as claimed in claim 1, whereinsaid concentrated cleaning composition in step (d) is diluted with waterin the ratio of from 1:8 to 1:10 of said composition to water.
 4. Aprocess, as claimed in claim 3, wherein said diluted compositionexhibits a pH in the range 9 to
 10. 5. A process, as claimed in claim 1,wherein said liquid soap and potato digest in step (c) are admixed in aweight ratio of 60:40.
 6. A process, as claimed in claim 1, when in step(a) 9 to 11 parts by weight dry caustic is mixed with each 100 parts byweight dry potato solids in the potato processing wastes in the presenceof 40 to 60 parts by weight water per 100 parts by weight dry potatosolids.
 7. A process, as claimed in claim 1, wherein where in step (b)said fatty acid source is heated to 135° - 150° F. prior to reactionwith said alkali.
 8. A process, as claimed in claim 7, wherein 9 to 11parts by weight dry caustic is reacted with each 100 parts by weightfatty acid source in the presence of 25 to 28 parts by weight water per100 parts by weight fatty acid source.
 9. A process, as claimed in claim1, wherein said fatty acid source in step (b) is potato processing wasteoils.
 10. A process, as claimed in claim 1, wherein said heating in step(d) is accomplished at 212° F. for about 30 minutes and an oxygencontaining gas is bubbled therethrough.
 11. A process, as claimed inclaim 1, wherein said admixture in step (d) is mechanically agitatedduring heating.
 12. A process, as claimed in claim 1, including thefurther step of removing solid residue from said concentrated cleaningcomposition following heating.
 13. A process, as claimed in claim 12,wherein said solid residue removal is accomplished by filtration.
 14. Aprocess, as claimed in claim 1, wherein one pound of said alkali isadded for each 10 pounds of concentrated cleaning composition; saidmixture is diluted with about 25% of its own volume of water; and saidaqueous mixture is boiled for about 12 to 15 minutes.